I. Field of the Invention
The present invention relates to a posterior chamber implant for use after extracapsular surgery.
II. Description of Related Art
In extracapsular surgery, a surgical opening is formed through the front membrane of the lens of the human eye and the cataracts and the fluids within the interior of the lens are then surgically removed. During such surgery, the posterior capsule of the lens is usually left intact so that it forms a barrier between the vitreous humor and the aqueous humor in the eye.
After removal of the cataracts and other material within the original lens, it is necessary to replace the eye lens with an artificial lens implant in order to restore sight to the eye. Although such artificial lenses have in the past been placed in the anterior chamber, it has been found that placement of the artificial lens in the posterior chamber, i.e. in the lens sack, is superior for many reasons.
These previously known posterior chamber lens implants typically comprise a lens having a convex front surface and a planar or concave rear surface. Two or more haptics are then secured to the lens in order to center and attach the lens in the lens sack.
A primary disadvantage of many of these previously known posterior chamber lens implants, however, is that such lens implants are only capable of restoring far vision for the patient, especially when the patient is of middle age or older. For such patients, the previously known posterior chamber lens implants do not restore near vision of the type necessary for reading. Consequently, patients who have undergone lens implantation surgery must still wear reading glasses to read even though their far vision is restored.
There have, however, been attempts at the multi-focal lens implants, i.e. lens implants that would restore both far and near vision. In one such previously known multi-focal lens, concentric rings are formed on the lens to achieve both near and far vision.
A primary disadvantage, however, of these previously known multi-focal lenses is that such lenses are particularly susceptible to glare, particularly at night. Consequently, such multi-focal lenses have not achieved widespread use or acceptance.